Waste heat economizer



Patented Feb. 18,1194? v i 2UNlTF-A). STATES vPATENT OFFICE WASTE HEATECoNoMlzEn .Y r i John S. Wallis, Darien, ,and John W. Throcki morton,Wilton, Conn., assignors to Petro- Chem Process Company, Incorporated,New

` York, N. Y., a corporation of Delaware Application April 29, 1944,serial 1'\ro.`5e3,420` n, n

This invention relates td heat exchange apparatus and refers moreparticularly to waste heat-y economizers wherein flue gas or exhaustvrgases from which the heat has beenlpartially spent-l or i exhausted isyutilized to heat fluids passed in heat exchange relation therewith.

Exhaust gases from internal combustion engines,V furnaces of ydifferenttypes such as rotary retorts for the manufacture of cement, steel millfurnaces, furnaces" for heatingfboiler water and flue gases from othersources containing varying amounts of Vwaste heat may serve to supplythe necessary waste heat to the economizer.

Thevnovelty in the` invention resides primarily in the followingstructural features:

1,"Arrang`ement of the heating space and tuy bular heat exchangeelements to produce a minl imum pressure drop between the inlet andoutlet ports, ory a minimum -backpressure to the passage of the heatinggases (vertical chamber with vertical tubes and uplow of gases);

2. Utilizing extended surface -on the tubes to increase heat exchangeefficiencies and locating the extended surface centrally of`theheater'in order to expose bare surface tubes .adjacent theinletandoutlet ports, thereby obtaining more evendistribution of the heatinggasesvover the exchange surface and better heat distribution.

3. Enclosing the heating chamber at the top and bottom by upperandlowerv tube sheets, supporting the tubes on the lower tube sheet andpreventing displacement and limiting the relative movement of the tubesby guides at their upper ends for connecting the tubes by removable.return bends in order that single tubes or sets of tubes may-be'iremoved through the top of the chamber without disturbing the vsidewall insulation.

A further object ofthe invention is to provide a waste heat economizerwhose heat exchange surface has approximately six timesV thev capacityof bare tubes without the surface. This gives efficient duty with asmall .number of tubes, effecting substantial economies in both size andweight of the structure. For example,van economizer having twenty`extended surface tubes of the type shown will `deliver the service ofapproximately one hundred bare ytubeheatin'g elements and the weight ofthe bare tubestructure 4would, be` four times as great. This low Weightf is of particular` importancewhere` economizers are installedv inelevated positions, such as in the `stacks or viiues of power plants',steam ships` and in other places where weight is an' important factor.In certain types of catalytic cracking i 1 claim. (crema-223) units theiiue gas leaving the catalystchamber may be elevated l feet ormorefand alight weight economizer' naturally reduces the amount of supportingsteel structure required. l Further advantages and novelty will beapparent from the following description.

In the accompanying drawings which form a part of thefinstantspecification and are to be read in conjunction therewith, and in whichlike numerals fare used to indicate like parts in the various views, i yf Fig.l 1 is a side elevational viewof an economizer embodying thevinvention connected to an existing furnace and stack installation;

Fig. 2 is a vertical sectional view of theA economizer shown in Fig. 1;l Fig. 3 is a view taken along the line'B-I in Fig. 2 in the directionof the arrows; f V

Fig. 4 is a sectional view t ken along the line 4--4 inFig. 2 in thedirection of the arrows;

Fig. 5 is a partial view of the top of an econ l shown inFig. 6. y gReferring to the drawings andparticularly to Fig. 1, at l0 is shown adiagrammatic furnace or ovenv having la flue gas outlet Il. This outletue VIl is connected to the inlet I2 ofthe economizer by a flanged ringshown in Fig. 2. The

4K0 economizer comprises an outer sheet metal cas.V

ing- I3 lined with refractory material I4 capable f oi' withstanding andresisting withoutsubstantial deterioration the ue gases passingtherethrough. The heating space of the economizer shown in Fig. 2is-closed at thel top by a removable cover plate I5.k Thev heatngfspacein Athe economizer shown in Fig. f6 is enclosed at the top by a tubesheet divided into a plurality of segments I6. The edges'of theysegments `arecut out to fit the `exterior surfaces of the pipes.

the radially extending separating lines between the segments to passIthrough the center of the pipes which they bisect. Also in the typeKVshown in Fig."6 above the segmental tube sheetk is'lan "ong the une1;-1 in SUP-r ports and tube guides used in the economizer Thesesegmentsare made removableby locating Y `return bends 24.

. ends providing continuous passage for the fluid through the tubes.They also have plugged openings in axial alignment with the tubes,permiti ting the tubes to be cleaned from below when the plugs areremoved; The tubes are serially connected so that liquid introducedthrough pipel 25 is directed through the tubes in a continuous passageto the discharge pipe 26. 'I'he'upper extremities of the tubesdesignated by the numeral 22a and on those portions of the tubes `whichlie 'adjacent the outlet opening 21 of the heating space are withoutfins. yCorrespondingly, those portions of the tubes designated by thenumeral 22h which are adjacent the inlet opening I2 are likewise baresurfaced except for tube support members hereinafter described.

Ailixed to the exterior of the tubes between the upper and lowersections without ns are the iin vtube sections of ythe heating elementsdesignated by the numeral 22c. The iin surface sections of the tubes arepositioned centrally within the heating space of the economizer betweenthe inlet and outlet ports. The extended surface or longitudinal finsaiiixed to the outer surfaces of the tubes expose a greatly enlargedsurface' for the transmission of heat from the heating gases to thefluid passing through the tubes. The fins are U-shape in cross sectionwith the ybases of the U-shape members welded to the tube surfaceforming an integral structure and one well adapted for the transmissionof heat energy. Lying parallel with the tubes theyoiiera minimum of4obstruction to the passage of the gases. One set of fins on oppositesides ofthe pipe are extended downwardly from the fin tube section tothe lower tube'sheet-as shown in Figs. 2 and 4. These iins are numbered22d andare "shown in cross section in Fig. 4. Their lower ends seat uponthe tube sheet I9 and serve as a support for the individua1 tubes. Beingpositioned on opposite sides of the tubes andv in alignment withthepassage of the gases entering through inlet I2 they offer a minimumresistance to the gas oW. f 3,

Inorder to hold the'tubular heating elements in spaced relation andprevent displacement due to warping or uneven heating, the upperinverted l U-bends 23 are hung upon cross strips or channels 28 .bymeansof U-shaped hanger bolts 29.`

i tube sheet I9 to support the weight of each pair of tubes to which itis connected.v The upper ends mittedv to uniformly distribute themselvesthroughout the lower portion of the economizer. The gas passage isthence upwardly along the channels formed by the dns surrounding thetubes where the greater part of the heat is transmitted from the gasesto the fluid within the tubes. In their passage from the bottom to thetop ofthe economizer there is but little pressure drop due to the lowfriction resistance caused by the absence of any bales and no changes inthe direction of the flow of the flue gas. It will be notedl thathorizontal baffles have been entirely dispensed with, the magnitude ofthe'surface ex posed being relied upon to extract the principal part ofusable heat from the gases. At the top of the economizer and oppositethe outlet duct 21 the tubes are again without iin surfacescorresponding to the space opposite the inlet port permitting freedischarge of the `gases through vthe outlet opening with a minimum ofresistance afforded by the tube surface.

In both types of economizers the tubes can beI easily removed from theheating chamber without disturbing the insulation or refractory liningexcept such refractory material as may surround the lower ends of thetubes above lthe tube sheet.

To remove the tubes from ther economizer shownin Fig. 2 it is onlynecessary toremover the lower double closure return bends 24, take ofi'the top Acover plate I5, remove the top hangers and supporting stripsand raise the tubes from the chamber.

To remove tubes from theA economizer shown` in Fig. 6 the top doors I1are opened, the upper segmental tube sheet/I6 is removed and one or moreof the return bends 32 taken from the pipes.

This permits the tubesto be raised vertically from the heating chamberif the lower p1ugs3l have been previously taken out of the bottornfheaders. YLikewise in cleaning the tubes in the economizer shown in Fig.6 the U-bends at the top are removed, the lower plugs are ktaken out andthe tubesreadily cleaned from above. In cleaning the tubes of theeconomizer shown in Fig. 2 the plugs are removed from the lower returnbends and a cleaner inserted from below.

vThe tube cleaners are sufficiently viiexibleto re move accumulatedmaterial from the top re,

turn bends when the tubesV are cleaned from below.

` Although the description of the economizerhas been based on utilizingfin tube extended surfaces, it is contemplated as. well to use othertypes of extended surface such as spiral fins, pin type surface or lanytype of extended ksurface which is bonded integrally to the heatingelement. Furthermore, although the drawings shown have been based on aseries iiow through the heating elements, it is contemplated that theheater arrangement may bev modified so that either series or multi-passiiow may be utilized, depending upon the quantity of the product beingtreated and the pressure drop requirements.

From the foregoing it will be seen that the invention is well adapted toattainall of the ends and objects hereinbefore set forth together withof the adjoining tubes in this modification are f connected by a'removable return bend 32 shown ink detail in Fig. 9. In operation bothtypes of economizers function the same. l Waste heat gases areintroducedthrough iiue Hand inlet I2. Due

to the plain surface sections oi' the lower extremi- 1 tiesof the tubeswithout. fins the gases are per- 'other advantages which are obvious andwhich are inherent to the structure. As many possible embodiments may bemade of the invention without departing from the scope thereof,V it isunderstood that all matter herein set forthvor shown in the accompanyingdrawingsv is tobe linterpreted as illustrative andnoti'n a limitingsense.

Having thus described our invention, we claim: Y A waste heat economizercomprising a vertical chamber, a plurality of vertical tubes'connectedin series within thevchamber to form a continuous passageway for iiuldto be heated, heating gas inlet and outlet ports in the chamber,

a lower tube sheet supporting the tubes, iongi- 5 tudinal ns on thetubes intermediate the inlet i and outlet parts serving to increasetheir `heat exchange surface and spacer members engaging the tubesadjacent their uppor portions to Vhold them iny spaced relation withrespect to each other and in position in the heating chamber.

.I oHN s. wALms. i 4JOHN W. THRocKMoRToN.

n r l 1 "q o REFERENCES CITED The following references are'of record inthe Number 1i Number n le of .this patent:

\ UNITED STATES PATENTS Name Date Luckev Oct. 25, 1932 McCausland Aug.1, 1933 De Fiorez Jan.` 29, 1935 Alther June 1, 1937 Throckmorton Mar.17, 1942 FOREIGN PATENTS Country Date German Feb. 10, 1928

